Over the past few years, the use of CMOS image sensors has proliferated into a variety of user models. The most notable is its acceleration in the consumer handheld imaging space as a standard feature on the mobile phone. As time has progressed, the resolution and quality expectations of the consumer have increased at a remarkable pace. Only a few years ago the presence of a VGA or QSXGA image sensor mobile phone was considered a novelty. In today's market place, expectations are increasing to high megapixel counts in the 3.1 to 5 MP range. All indications are that the resolution will go much higher and solutions which realize 12 to 16 MP will become commonplace. In addition, the expectation is to provide print quality imaging capability competitive in quality to a digital still camera (DSC) and also to capture high quality HD video ready for display on a HD TV.
In order to address the increases in resolution with the form factor restrictions, the sensor manufacturers are aggressively shrinking pixel size. Today, it is common to see pixels with 2.24 um size; in the future the size may drop to as low as 1.1 um and smaller. This reduction in pixel size allows higher megapixels to be achieved in smaller optical formats. However, the reduced active photosites aggravates the signal-to-noise-ratio (SNR) of the sensor and the ability to collect photons and thus operate in coveted lowlight environments effectively.